Overnight in dozens of cities across the U.S., the electric scooters arrive, often without warning to public officials, parked along sidewalks and ready to be taken for a spin with a few taps on a smartphone. It's not long before they attract attention – and it's not always positive:

San Francisco is ordering three companies that began renting motorized foot-pedal scooters in the city last month to stop operating until they can ensure riders are obeying state laws and that the devices are not a hazard to the public.